122ANATOMY,formed of two curved cells whose concavities face each other. These two small Up-like ceUs are termed stomata. Stomata, though epidermal organs, differ from theepidermis in that their cells are much smaller, and nearly always situated belowthose ofthe epidermis ; they further present different contents, and especially granulesof chloroph3dl; whence they may be regarded as intermediate between the epidermisand the subjacent parenchyma. Stomata are variously distributed over the surface ofthe leaves : usually solitary, often arranged in series, some¬ times crowded in the base of a cavity (as in some Proteacew, figs. 678, 679). Their number varies: the Iris contains 12,000 in a square inch; the Pink, 40,000; the Lilac, 120,000. When moistened, their lips swell and become more curved, and hence gape; when dry, they shorten and close. Stomata always correspond to intercellular passages, and are found on theordinary leaves of Phsenogams, principally on their lower surface, on stipules, on herbaceous bark, calyces, and ovaries; they are wanting on roots, rhizomes, non- foliaceous petioles, most petals, and seeds; acotyledons, and submerged aquatic plants, which have no epidermis, equally want stomata. If a fragment of a stem or leaf be macerated, the cellular tissue beneaththe epidermis is rapidly destroyed, and the latter divides into two layers, anexternal epidermis proper, and a very thin membrane (fig. 680), moulded on theepidermis and extending even over its hairs, which are sheathed in it like fingers ina, glove (p) ; it presents openings (p) corresponding to the stomata. Brongniart hascalled this membrane the cuticle (little skin); it is not ceUular, like the epidermiswhich it covers.678. Vertical section of pari of a Banksia leaf (mag,).'679. Part of a Banksia leaf, presenting three sections pai-aUel' to the lower sur¬ face, and at different depths (mag,)."680. Cabbage. Cuticle. ' Fig. 678 is a section perpendicular to the thicknessof the leaf, showing: 1, on the upper and lower facestwo layers of epidermal cells ; 2, fibro-vascular bundlesto the right and left, cut perpendicularly to their length;3, on the lower face, a depression, clothed with hairs,and pierced by stomata which communicate with theinterstices of a very loose cellular tissue. Above this'tissue, the upper half is a mass of elongated and erectcells, perpendicular to the epidermis. '' Pig, 679. Three sections parallel to the plane of theleaf, carried through three such depressions, each circum¬scribed by the fibro-vascular bundles of the nerves. Inthe cavity at the bottom of the figure, the section hascarried away the hairs clothing the walls of the depres¬sion, leaving. the stomata and epidermal cells visible;in the cavity on the right the loose cellular tissue ¦whichunderlies the stomata of the epidermis is seen throughthe latter; in the third depression the section has re¬moved all but this subjacent tissue with its intercellular